Actin and Cytokeratin in Superficial Transitional Epithelial Cells of the Rabbit Urinary Bladder : A Confocal and Electron Microscopic Study
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Transitional epithelial cells undergo dynamic morphological alterations during the contraction-expansion cycle in the mammalian urinary bladder. In this study, the localization of two major cytoskeletal elements, actin and cytokeratin, was examined by fluorescence and electron microscopic methods to elucidate the relationship of these components in the transitional epithelial cells of non-distended bladders. Using phalloidin-FITC and confocal laser scanning microscopy (CLSM), a strong staining for filamentous actin was observed at subplasmalemmal regions of the superficial cells. Cytoplasmic regions of these cells were characterized by punctate regions of staining that increased at sites of cell-cell contact. Ultrastructural observations using immunogold and heavy meromyosin (HMM) labelling techniques for detecting actin filaments revealed a rich actin filament network in superficial cells most notably in the subplasmalemmal regions. These filaments occurred in orientations that were both parallel and perpendicular relative to the surface membrane. Intermediate and basal cells contained a less dense network of filamentous actin in comparison to superficial cells. Immunolabelling for cytokeratin 18 revealed abundant thread-like filaments coursing throughout the cytoplasm and making contact with the plasmalemma in superficial cells. By electron microscopy, the cytokeratin filaments formed a dense interlacing network arranged into bundles that interconnected with membrane-bound structures. These observations indicate that actin and cytokeratin are major cytoskeletal elements of transitional epithelial cells and that they are related to the configurational alternations of transitional epithelial cell borders and their contents. It is postulated that these proteins stabilize and support the membrane of superficial cells from hydrostatic pressure within the bladder.
- ACTA HISTOCHEMICA ET CYTOCHEMICA
ACTA HISTOCHEMICA ET CYTOCHEMICA 30(1), 29-36, 1997-02-01
JAPAN SOCIETY OF HISTOCHEMISTRY AND CYTOCHEMISTRY